Recently there has been an increased interest in the generation of ceranlic powders
composed ofnanosize particles with a narrow size-distribution and high purity. It has
been shown that ceramics sintered from these ultrafine partic1es exhibit improved
mechanical and electrical properties. The present research has attempted to control the
growth of the ceramic particles in a relatively simple continuous flow process by placing
charges on the forming particles and controlling their evolution with an electric field.
Nanosize Ti02 powder was produced using a multi-stream, co-annular reactor.
The heat source was a cylindrical H2/02 diffusion flame located around the outside of
reaction zone. The effect on the powder size, shape, and size distribution due to particle
charging, applied electric fields, and varying reactant concentrations were investigated.
The temperature field within the reaction zone was uniform radially and ramped
axially from 600 to 1100 K. The reactant stream passed through a 10 millicurie Po-21 0
alpha source within the burner with the intention of creating a bipolar ion concentration.
In the presence of an electric field, this ionization can lead to either a unipolar-negative or
unipolar-positive particle charging environnlent. The electric field across the reaction
zone was varied in an attempt to control particle residence time.
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